With the ever increasing desire for faster data rates, notably through long-term evolution-Advanced (LTE-A) networks in Release 10, system designers have turned several different techniques such as multiple input multiple output (MIMO), cooperative multiple point transmission (CoMP) and carrier aggregation. Carrier aggregation increases bandwidth, and thus bitrate, by aggregating multiple carriers to form a larger overall transmission bandwidth. The explosive increase in mobile data consumption has led to a LTE deployment and carrier aggregation in the unlicensed spectrum (LTE-Unlicensed (LTE-U), with UEs using the LTE-U band referred to as License Assisted Access (LAA) UEs). With increasing carrier aggregation, the HARQ-ACK response may take up a large amount of overhead.
It would be desirable to minimize the HARQ-ACK overhead while maintaining HARQ-ACK performance.